Extract TIFF images from PDF without decoding

Question

With the help of iText 5 I would like to extract all TIFF images from given PDF file and save them as TIFF files. Examples and other posts ( 1 , 2 ) use the following method:

1. Create PdfImageObject from PDF stream which in line 189 decodes the image stream (if corresponding filter implementation is present).
2. Call PdfImageObject#getImageAsBytes() which returns JPEG (original), PNG (re-encoded) or TIFF (in case of 8 bits per pixel).

As a result TIFF image with 1 bit color depth is converted to PNG, which is not what I need.

Another approach would be to call PdfImageObject#getBufferedImage() which will decode the image in step (2) into raster and afterwards encode it again as TIFF using ImageIO.write(bufferedImage, "tiff", file) .

As one can see this is not efficient. Another solution shown in this post demonstrates how to save encoded TIFF image stream to file by prepending it a TIFF header – that is the solution I am looking for.

Can iText help here?

Answer 1

PDF images are not TIFF images.

PDFs however can contain images that use compression techniques that are also used in TIFF, eg Flate, CCITT, LZW, JPEG.